The present invention relates to a two part modular connector system for interconnecting a backplane printed circuit board to a daughtercard printed circuit board. More particularly, the present invention relates to an improved two part backplane connector system which provides a drop in replacement for a standard two part backplane connector system.
The current industry standard for a two part modular connector system for electrically coupling a backplane to a daughtercard is set in the United States by specification EIA/IS-64 from Electronic Industries Association. This specification sets out parameters for 2 mm, two-part connectors for use printed with circuit boards and backplanes. The international standard for such two-part connectors is set forth in IEC 1076-4-001 specification 48B.38.1. Both of these specifications define a daughtercard connector (free board connector) that includes female receptacle contacts and a backplane or motherboard connector (fixed board connector) that contains male pin contacts. A connector that contains female receptacle contacts is commonly referred to as a "socket" connector, and a connector that contains male pin contacts is commonly referred to as a "header" connector.
One of the most vulnerable aspects of a pin and receptacle contact system is that pin contacts may be permanently warped or bent out of alignment due to impacting an edge or other blunt surface of a plastic socket connector housing during mating of the socket connector with the header connector. Such damage to the pins of the header connector can occur when an attempt is made to mate two connector halves without achieving proper alignment between the socket connector and the header connector. Improper alignment between the header connector and the socket connector can be the result of many causes, such as using component parts that are out of the allowable design tolerance, printed circuit board bow or warpage, insufficient or excessive clearance in card slot guides, improper part orientation, or mishandling before attempting to mate the socket connector and the header connector. When improper mating occurs, repair of bent pins of the header connector often require shutting off power to, and then removal of, the printed circuit board containing the damaged components. If a header connector containing damaged male pins is on a backplane or fixed board connector, repair often requires complete system shutdown and dismantling which is time consuming and expensive. If the header connector is on a daughtercard or free board connector, however, as is the case in the present invention, repair of damaged pins is much simpler and inexpensive. Depending on the electrical design, such repair to a header connector on the removable daughtercard does not require a complete system power down. In addition, if the pin damage to the header connector is unserviceable and requires a complete board replacement, it is usually more expensive to replace a thicker, multi-layer backplane printed circuit board than it is to replace a daughtercard.
As discussed above, the standard specification for two-part connectors for use with printed circuit boards and backplanes specifies that a header connector is coupled to the backplane and a socket connector is coupled to the daughtercard. Therefore, if pins of the header connector are damaged, the standard specification for such two-part connectors often requires more expensive servicing than would be the case if the header connector was mounted on a daughtercard.
Therefore, one object of the present invention is to provide a two-part modular connector system fully compatible with the EIA and IEC specifications and which has the header connector mounted on the daughtercard instead of the backplane to facilitate servicing if repair to the header connector pins is required.
Another advantage of having a socket connectors on the backplane printed circuit board is to obtain an Underwriters Laboratories (UL) user accessible electronic equipment classification. There is a UL requirement that electrical contacts reaching certain voltage or current levels not be "exposed" on systems that can be upgraded or accessed internally by users. Since female receptacle contacts are individually isolated and covered by a thermoplastic socket housing, the receptacle socket contacts are shielded from access by a user, thereby facilitating compliance with UL requirements.
The present invention provides a two part, modular connector system having a basic grid spacing between contact tails of 2 mm. The connector coupled to the backplane PCB is a straight socket connector containing female receptacle contacts. The connector coupled to the daughtercard PCB is a right angle header connector containing male pin contacts. The contact tails on both the header connector and socket connector can be designed to accommodate either solder attachment or solderless compliant pin terminations to plated through holes of a printed circuit board. The connector system of the present invention is 100% footprint and card-cage layout compatible with existing EIA/IS-64 and IEC 48B.38.1 standards. The relationship between the corresponding printed circuit board locations is exactly the same as the standard specifications. The term "stub length" refers to the distance from the backplane PCB surface to the first row of plated through holes on the daughtercard. The stub length provided by the connector system of the present invention is identical to the EIA and IEC standard connector stub length. This stub length is an important electrical parameter because it affects the overall electrical signal travel distance on the system bus and influences other electrical characteristics such as electrical path resistance, propagation delay, skew, impedance, etc.
Another important design requirement of two part connector systems is that of adequate plastic engagement or alignment before the electric contacts begin to mate. This is required in order to minimize potential bent pin problems as discussed above. In the standard EIA/IEC connector design, this engagement is accomplished by providing relatively high header walls that extend substantially above the pin contacts contained within these walls. (See FIG. 5 below.) This assures that the header connector and socket connector bodies will align themselves before contact engagement occurs.
An inverse connector configuration of the present invention which is also required to be compatible with this EIA and IEC layout standard, is significantly limited in the plastic-to-plastic engagement that can be achieved by using header walls to align the socket body before the electrical contacts interact. This difficulty arises because in the standard EIA and IEC design, a portion of the daughtercard actually becomes contained within an interior region between the header walls along the socket connector. With an inverse connector configuration of the present invention, this partial printed circuit board containment within the header connector is lost. In essence, layout compatibility forces the height of the inverse header connector walls and the overall height of the inverse socket connector to be significantly reduced.
The present invention provides an alternative method for generating plastic-to-plastic engagement without compromising compatibility with the modularity, layout geometry, and end-to-end stackability of the EIA/IEC design specification. A guide post feature was designed into the inverse two-part connector system of the present invention. The guide posts project in a cantilevered fashion from one side wall of the socket connector and are designed to fit within slot openings formed in a mating wall of the header connector. The guide posts accomplish the plastic-to-plastic engagement and alignment of the header connector with the socket connector before there is any electrical interaction between the pins of the header connector and the receptacle contacts of the socket connector. Therefore, plastic-to-plastic engagement is provided without compromising layout compatibility, end-to-end stackability, or modularity. The guide posts of the present invention advantageously provide alignment between the header connector and the socket connector without the loss of contact position and without requiring the use of additional printed circuit board real estate.
Another object of the present invention is to provide an inverse two-part modular connector system for coupling a daughtercard to a backplane which is 100% layout compatible with specifications EIA/IS-64 and IEC 1076-4-001 48B.38.1.
Other inverse 2 mm grid, two-part connector components are known. However, these components are not 100% EIA/IEC layout compatible. These known connectors do not retain the stub length dimension set forth in the EIA/IEC specifications. Particularly, the standard stub length dimension of 17.0 mm is determined by adding the "M" dimension as described in pages 14 and 15 (M=13.0 mm) of the IEC document, to the 4.0 mm distance from a mounting peg hole in the daughtercard to the first row of plated through holes in the daughtercard as described on pages 42-44 and FIGS. 32-36 of the IEC specification. Other inverse connector designs require that the daughtercard be located at least an additional 3.0 mm above the backplane surface. See for example, the Souriau Millipacs 1 and Berg METRAL connectors. This stub length differential prevents these designs from being a "drop in" replacement to backplane and daughtercard cage layouts which use the standard EIA or IEC two-part connector specification. These known components are intended for parallel stacking (Souriau Millipacs 1) or for cable-to-board (METRAL) applications, and are not designed to be drop in replacements for standard EIA/IEC specified backplane designs.
According to one aspect of the present invention, an electrical connector system is provided for coupling a first printed circuit board to a second printed circuit board. The connector system includes a socket connector having a housing formed to include an array of pin-receiving windows therein, and a plurality of receptacle contacts located within the housing in alignment with the pin-receiving windows. The receptacle contacts include tail sections electrically coupled to the first printed circuit board. The socket connector also includes a plurality of cantilevered guide posts extending away from the housing. The connector system further includes a header connector having a housing and an array of contact pins secured in the housing for engaging the receptacle contacts of the socket connector. The contact pins include tail sections electrically coupled to the second printed circuit board. The housing of the header connector is formed to include a plurality of guide slots aligned axially with the cantilevered guide posts formed on the socket connector. The guide slots are configured so that the guide posts enter the guide slots as the socket connector and the header connector are mated to align the array of pin-receiving windows of the socket connector with the array of pins of the header connector.
In the illustrated embodiment, the cantilevered guide posts formed on the socket connector include a generally rectangular body portion and a head portion having a pair of opposed ramp surfaces. The opposed ramp surfaces facilitate insertion of the guide posts into the guide slots of the header connector.
According to another aspect of the present invention, a modular connector system is provided for electrically coupling a fixed backplane printed circuit board to a removable daughtercard printed circuit board. The connector system includes a socket connector having a housing formed to include an array of pin-receiving windows therein, and a plurality of receptacle contacts located within the housing in alignment with the pin-receiving windows. The receptacle contacts include tail sections electrically coupled to the backplane. The connector system also includes a header connector having a housing and an array of contact pins secured in the housing for engaging the receptacle contacts of the socket connector. The contact pins include tail sections electrically coupled to the daughtercard. The socket connector and header connector are configured to provide a stub length of 17.0 mm between the backplane and the daughtercard upon insertion of the header connector into the socket connector.
In the illustrated embodiment, the header connector includes a peg for engaging an alignment hole formed in the daughtercard to position the alignment hole of the daughtercard 14.0 mm away from a top surface of the backplane upon insertion of the header connector into the socket connector. A top surface of the daughtercard is spaced apart from a first row of the array of contact pins of the header connector by 1.5 mm.
According to yet another aspect of the present invention, a modular connector system is provided for coupling a fixed backplane printed circuit board to a removable daughtercard printed circuit board. The connector system includes a socket connector having a housing including a top surface formed to include an array of pin-receiving windows therein and a side wall generally perpendicular to the top surface. The socket connector also includes a plurality of receptacle contacts located within the housing in alignment with the pin-receiving windows. The receptacle contacts including tail sections electrically coupled to the daughtercard. The socket connector further includes a cantilevered guide post having a proximal end formed integrally with the side wall of the housing and a distal end extending upwardly away from the side wall of the housing. The connector system further includes a header connector including a housing having first and second spaced apart side walls defining an interior region therebetween. The header connector also includes an array of contact pins secured in the housing and located within the interior region for engaging the receptacle contacts of the socket connector. The contact pins include tail sections electrically coupled to the second printed circuit board. The first side wall of the housing of the header connector is formed to include a guide slot having a first slot portion formed in the interior region and a slot opening extending through the first side wall. The guide slot is aligned axially with the cantilevered guide post formed on the socket connector. The guide slot is configured so that the guide post engages the first portion of the guide slot in the interior region as the socket connector and the header connector are mated to align the array of pin-receiving windows of the socket connector with the array of pins of the header connector. The distal end of the guide post extends through the slot opening in the first side wall of the header connector to lie outside the interior region of the header connector upon insertion of the header connector onto the socket connector.
Additional objects, features, and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of a preferred embodiment exemplifying the best mode of carrying out the invention as presently perceived.